Perpendicular magnetic recording has been developed in part to achieve higher recording density than is realized with longitudinal recording devices. A PMR write head typically has a main pole layer with a small surface area (pole tip) at an ABS, and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through the pole tip and enters a magnetic recording medium (disk) adjacent to the ABS. Magnetic flux is used to write a selected number of bits in the magnetic recording medium and typically returns to the main pole through two pathways including a trailing loop and a leading loop. The trailing loop has a trailing shield structure with first and second trailing shield sides at the ABS. An uppermost (PP3) trailing shield arches over the driving coil and connects to a top yoke that adjoins a top surface of the main pole layer near a back gap connection. The leading loop has a leading shield with a side at the ABS and that is connected to a return path (RTP) proximate to the ABS. The RTP extends to the back gap connection (BGC) and enables magnetic flux in the leading loop pathway to return from the leading shield at the ABS and through the BGC to the main pole layer. Magnetic flux is able to flow through the leading loop and trailing loop.
The double write shield (DWS) design that features the leading and trailing loops was invented for adjacent track erasure (ATE) improvement by reducing stray field in side shields and in the leading shield. Accordingly, a PMR head has a great advantage over LMR in providing higher write field, better read back signal, and potentially much higher areal density. With the growing demand for cloud storage and cloud-based network computing, high and ultra high data rate recording becomes important for high-end disk drive applications.
To achieve areal density in a HDD beyond 2 terabytes per platter (TBPP) for conventional PMR, dual writer designs have been proposed where the better of the two writers is determined during back end testing, and then the better writer is integrated in a HGA. One problem with this strategy is that the better writer is not selected before spin stand dynamic performance (DP) testing is completed. In other words, the ABS pattern needs to be applied before the spin stand DP data is generated. This process implies a head is predetermined to be up facing (UP) or down facing (DN) before DP testing, and during slider fabrication when the ABS pattern is completed. Currently, the ABS pattern is the same for UP and DN heads except one is the mirror image of the other. Thus, an UP head will pair with UP suspension and a DN head will pair with DN suspension at slider fabrication. Unfortunately, during a write process with OD skew, RWO will increase and ADC will degrade if the better writer has an unoptimized head orientation. Therefore, an improved dual PMR writer scheme is needed to ensure that the selected (better) writer has a head correctly configured UP or DN after the slider is formed on the suspension to provide a minimum RWO and maximum ADC at OD skew.